The present embodiments relate to positron tomography. In positron emission tomography (PET), a radiopharmaceutical is placed within a patient. The radiopharmaceutical tags particular biological function. Positrons emitted by the radiopharmaceutical at the tagged locations interact with nearby electrons, causing detectable radiation. The PET scanner detects the annihilation events. Using tomography, a distribution of rates of annihilation is created. This reconstruction represents the tagged biological activity in the patient, but provides little information about the tissues of the patient other than biological activity.
PET may be combined with another imaging modality in a hybrid system. The other modality provides additional tissue information. PET/computed tomography (CT), single photon emission computed tomography (SPECT)/CT, and PET/magnetic resonance (MR) multimodality imaging systems allow scans to be performed back-to-back or in a same coordinate system and similar timing. The axial fields of view of the individual modalities are as close together as possible in order to minimize the impact of patient motion and increase correlation of the respective data sets. While the CT or MR may provide different tissue information than PET or SPECT, further information may assist in diagnosis.